The present disclosure is related to an unevenness inspection apparatus and an unevenness inspection method for carrying out an unevenness inspection (color unevenness inspection and luminance unevenness inspection) in color images and the like.
In the past, a color unevenness or a luminance unevenness inspection in mass production lines of display units using CRTs (Cathode Ray Tubes), LCDs (Liquid Crystal Displays), and the like that are allowed to display color images has been mainly performed utilizing a sensory test based on a comparison with a limit sample. This technique, which is achieved in such a manner that a display screen on a display unit targeted for inspection is directly viewed by a human, provides an inspection similar to actual status of use, and a simple testing method.
However, such a technique depends mostly on the ability of an individual inspecting staff, and thus the inspection quality is influenced by a individual difference among inspecting staffs or a fatigue level of an inspecting staff, which makes it difficult to assure a stable inspection.
To deal with such an issue, several objective color unevenness inspection techniques that are independent of the ability of an individual inspecting staff have been proposed. Examples of such a technique include a technique wherein the hue in a plurality of locations within a display screen is measured using color image pickup device and the like with an overall display screen set up in a white-color display state to carry out a color unevenness inspection according to a magnitude relation of values of a maximum color difference from that of white-color display portions (Δ Euv* or Δ Eab*).
In concrete terms, for example, Japanese Unexamined Patent Application Publication Nos. 1989-225296, 1998-2800, and 2003-57146 measure the color and brightness in several locations within a display screen, and standardize a variation or a difference from a maximum value and a minimum value for use in the color unevenness inspection. Further, for example, Japanese Unexamined Patent Application Publication No. 1998-96681 pays attention to a spatial size of a color unevenness region or a color-varying region, quantifying these for use in the color unevenness inspection. In addition, for example, Japanese Unexamined Patent Application Publication No. 2007-198850 proposes a technique to evaluate a luminance unevenness for each luminance data of R (red), G (green), and B (blue).